1. Field of the Invention
This invention relates to fuzzy computers, fuzzy processors, fuzzy controllers, and MAX circuit composite devices, along with circuits used in same, including grade-controllable membership function circuits, grade-controllable membership function generator circuits, and center of gravity determination circuits which act as useful circuits for defuzzifiers which convert fuzzy quantities into definitive values.
2. Prior Art Statement
A great human mind created the digital computer through the harmonization of the elements of the concept of the stored program, Boolean algebra and binary hardware which carries out stable operations. Iteration of these operations makes possible the development of complex logical structures and complex data processing techniques and the like. The stability of these operations gives the digital computer excellent reliability, so digital computer systems are becoming larger and larger. As long as the program does not include any human mental information, digital computers can run any type of program, hence their appellation as the "universal machine." The appearance of the digital computer system is having profound effects on the everyday life and culture of man.
Another great human mind created an extremely important concept, that of "fuzziness" through the study of how man thinks and how men communicate between themselves. L.A. Zadeh proposed the concept of the fuzzy set in 1965. Since then, while there have been many papers published on theoretical studies of fuzziness, there have been few reports on its practical application, and in fact, such work has only been carried out with the help of binary digital computers.
Research into fuzziness has emphasized that human knowledge is based on accumulated experience which is summed up as linguistic information such as expert knowledge. This linguistic information is generally endowed with vagueness, ambiguity, inaccuracy, and incompleteness so it can be characterized as membership functions. The size of the membership can be expressed by numerical values in the region from 0.0 to 1.0, varying within this range.
For linguistic information to be handled by a digital computer, the size (value) of the membership is represented by a binary code. In binary electronic circuits, this value represented by binary code is repeatedly stored, transferred and finally calculated over and over according to a stored program. Thus there is a problem with the processing of fuzzy information by digital system in that they require large amounts of time to do so. In addition, the binary-coded values require incredibly large amounts of storage and vast numbers of devices used for calculation. While the digital computer is a universal machine as described above, it is not necessarily most suited for the realtime processing of fuzzy information. This has prompted searches for other types of machines which can efficiently process fuzzy information at high speed.
Recent fuzzy computer systems represent fuzzy information including fuzzy membership functions, results of fuzzy inferences and such as electrical signals (voltage or current) distributed among a plurality of lines. One often needs to select a single definitive value from the fuzzy information represented by an electrical signal distribution provided as output from fuzzy controllers or fuzzy computers. The circuits which convert fuzzy information to definitive values are called defuzzifiers, an example of which is a center of gravity determination circuit.
A center of gravity determination circuit typically comprises multiplication circuits, addition circuits and division circuits. The hardware for such multiplication circuits and division circuits is complex and not readily adjustable, while they are also limited in dynamic range.